Does anyone happen to know what the stock/factory headgasket thickness is by any chance? Thanks in advance.....

98eldo32v

02-16-11, 04:29 AM

I guess this one is a stumper..... I'll have to measure a stock gasket when I get a hold of one....

Submariner409

02-16-11, 09:06 AM

Not in the service manual or alldata. Most stock graphite/metal sandwich gaskets are something like .080" - .100" new, .040" - .050" compressed. For a Northstar, which has minimal deck clearance (.017"), that .040" in the quench areas is the source of the "cold carbon rap". The absolute maximum head cleanup cut is .007", so GM doesn't want compressed gasket thicknesses to get too thin.

You might get in touch with Cometic and ask for their MLS thickness for a Northstar. MLS gaskets do not, for all practical purposes, compress.

OK, it took 34 seconds - The Cometic MLS for Northstar is .066" new. Around $175 each.

98eldo32v

02-16-11, 09:56 AM

Thanks Sub,

I had researched the Cometic MLS gaskets and saw the .066 listing.

I called a vendor and asked what was the stock replacment thickness and he stated the .066 was the replacement. Yet, that got me wondering was the stock gasket the same thickness? How do I know for sure that I'm not lowering/ raising my compression without a reference number to go by?

I figured with all the headgaskets being done now and before me that this topic had to come up.

I guess I'm over analyzing again......

Submariner409

02-16-11, 10:06 AM

FelPro (Federal Mogul) and other gasket makers will stick darn close to the stock engine designer's compressed gasket thickness specs. You really need to change gasket thicknesses radically to make any significant compression ratio change.

An off-the-shelf FelPro gasket set, bought in January, for one of my (1970 ?) 455 Olds engines comes out at exactly the 1970 compressed specs for a 10.5:1 engine - .040". BUT, we don't want a working marine engine to run at 10.5 or 11:1 so we use dished pistons to lower the CR to < 10:1.

98eldo32v

02-16-11, 10:47 AM

Thank Sub for the info, it's always greatly appreciated.....

98eldo32v

02-16-11, 10:50 AM

Has anyone on here used the cometic mls gasket? What were your findings? Was it worth the money is going that route?

98eldo32v

02-18-11, 03:32 AM

Well, I just ordered the felpro set for my eldo.

I wanted to go the cometic route mls head gasket, but I needed all the other gaskets rounded up too.

Rock Auto had the head set for 169.99. There was some promotion code to save 5%. In all it came 169.80 shipped fedex or ups ground.

I've used rock auto before, they are pretty quick with shipping.

I just have to get another oil pump, gm rear main seal, front crankshaft seal.

The mid seal on the sts donor engine is bone dry, so I don't have to mess with that(thank the Lord). I may take the oil pan off to reseal that.

I really don't wish to disturb the bottom end if I really don't have to.